Abstract Developmental language and communication disorders have detrimental effects on multiple aspects of children?s lives including social/behavioral development, academic achievement, and vocational outcomes. Developmental language disorder is a high prevalence condition that constitutes a significant public health concern. In order to develop sensitive assessment measures and effective treatments, it is essential to have a clear understanding of the nature of this disorder. Although there are some epidemiologic studies of child language disorder, most of what we know about this disorder has been gained from convenience or clinical samples that can be fraught with confounds. More population-based research of communication disorders is needed, especially within the United States. One notable gap in the literature pertains to the new DSM-5 category of Social (Pragmatic) Communication Disorder (SCD). SCD is defined as persistent difficulties in social use of verbal and nonverbal communication that leads to functional limitations in not only communication but also social, academic, and vocational domains. The proposed research will address the controversy about how best to assess SCD and will be the first study to estimate its prevalence within a population-based sample. The overall goal of this NIDCD Research Career Enhancement Award (K18) application by an established investigator is to gain advanced training in the field of epidemiology with a focus on language and communication disorders. The candidate has a strong record of extramural funding and scientific productivity in the area of child language disorders spanning more than 25 years. The specific objectives of this proposal include: 1) Strengthen knowledge of the field of epidemiology; 2) Obtain advanced training in design, methods, and analysis techniques for epidemiologic research; 3) Conduct a study to establish assessment criteria to estimate the occurrence of SCD in a population- based sample of school-age children and identify risk factors and sequela of SCD; 4) Begin to examine overlap and distinction among SCD and other communication and/or developmental disorders (i.e., autism) as a basis for future research. The training plan takes advantage of the rich community of epidemiologists at the University of Wisconsin-Madison; it consists of didactic coursework in the Population Health Sciences Department, weekly seminars, and various experiential activities. The proposed research will primarily be accomplished through secondary data analysis of a prior publicly available population sample of language disorders referred to as the EpiSLI Database. The EpiSLI study used carefully constructed and well defined criteria to investigate structural language disorder (vocabulary/grammar); therefore, it will be possible to provide new insights into the relation between structural language deficits and SCD. Finally, the longitudinal nature of the database increases the significance of this research by allowing examination of both risk factors and sequela of SCD.